Process of recovering tin



Patented July 20, 1926. i I

ELMO G. HICKEY, OF LOS ANGELES, CALIFORNIA.

PROCESS OF RECOVERING TIN.

Io Drawing.

This invention relates to process for recovering tin from tin cans,scrap tin and other tin surfaces.

For approximately the past fifty years various processes for the removalof tin from tin bearing scrap, tin cans and the like, have been knownand used. These processes have, for the most part, been based upon thefact that tin is soluble in either hot or cold solutions of causticalkali in the presence of alkali metal nitrates. These processes have,for the most part, a number of difiiculties, one of which difficultieshas been in thedevelopment of this recovery process from the standpointof com-.

mercial success because of the relatively long time required for thisaction to take place and the consequent excessive high cost in plantexpense, handling charges of any considerable quantity of material to bedetinned, such as tin scrap, refuse, tin cans, and the like.

An object of this invention is to provide a process by which the tin maybe recovered from tin scrap, refuse, tin cans, and the like, in arelatively short time, maintaining a high efliciency of the recovery ofthe tin.

I have discovered that the recovery of tin is greatly accelerated by,the addition of ammonia to the alkaline solution composed of causticsoda and alkaline nitrates. According to the preferred form of theinvention, the tin scrap, tin cans, and the like, properly cleaned andperforated, is sub-- jected to the action of a solution of caustic sodaand sodium nitrate to which from .3% to 3% by weight of ammoniumhydroxide has been added; the ammonium hydroxide used beingapproximately 28% NH The solution is heated approximately to boiling.This solution is from 4 to 12% sodium nitrate and from 18 to 28% sodiumhydroxide, although it is to be understood that other alkali-metalhydroxides might be employed Application filed April as, 1925. SerialNo. 26,524.

and that nitrates other than sodium nitrate mlght be employed in thisprocess with equal elficiency, sodium nitrate and sodium hy- "coveredthat the tin will be completely removed from the tin scrap withinapproximately an hour, where heretofore it has required from 6 to 7hours to obtain the same tin recovery.

Having fully described the preferred embodiment of this invention, it isto be under,- stood that this invention relates tovthe use of ammonia asa catalytic agent for accelerating the rate of recovery of tin from tinscrap and that the same is in no way dependent upon the percentages ofsodium hydroxides and sodium nitrate employed other than that the sameshould be of suflicient strength to remove the tin from the tin bearingscrap and precipitate the same, preferably as sodium stannate.

I claim:

1. A process of recovering tin from tin scraps which comprisessubjecting the tin scraps to the action of caustic alkali and alkalimetal nitrate in the presence of ammonia.

2. A process of recovering tin from tin scraps comprising subjecting tinscrap to the action of caustic alkali and alkali "metal nitrate in thepresence of from .3 to 3% of ammonia hydroxide containing 28% ammonia byweight. V 3. In a process of recovering tin from tin scraps, employingcaustic alkali solution, the step which includes the use of ammonia asan energizing agent.

Signed at Los Angeles, California, this 23d day of April 1925.

ELMO G. HICKEY.

